No justification was provided, no. Some comments speculated that it might have been something similar to what they practiced at British Railways or at many transit agencies in the former communist bloc, whereby if they couldn't repair a vehicle in time to appease the brass, then they would swap the number, i.e. if 4126 was in need of repairs and required by a certain time period, but was not finished, they would renumber 4158 to 4126 in its place, and 4126 would presumably take 4158's identity.
Somewhat conveniently, both cars are gone, so no one can check the builder's plates to verify if any skullduggery had taken place.

Does anyone know if it was a practice, at any point in the history of the CLRV, for cars to swap numbers?
A while back, in the Toronto Transit FB group, a TTC employee from Leslie Barns replied to a photo of 4126 by saying that that car used to be 4158. Now, this member was not known for posting trustworthy information (they previously claimed 4002 had been scrapped back in March, the day before the car returned to service, and when called out on it said that they were just messing with people), but I thought I'd ask here for a confirmation/denial of these claims. Thanks!

Where are you seeing that the only PCC they list as operational is 4000? If I go to their site I see all the usual suspects still listed.
https://hcry.org/portfolio_category/streetcar/
I was told that 4000 is way too old, fragile, and lacks commonality with the post-war cars for it to run on any kind of regular basis, so it would be very strange if that was the only PCC they kept running.

A TTC driver in the Toronto Transit FB group said that there are posted ALRV extras on the 511 for the June 23 board period.
Of course, whether the cars actually end up running there is another question. We've all seen what just happened to 4221, and it looks like 4207 hasn't run in a few days either?

On a less pleasant note, 4204 appears to have been shut off. Hopefully this isn't the end of the line for the car - I was personally hoping this one would be saved, being that it was the first one to run in service so many years ago.

If you're lucky you may spot the last remaining Boston CLRV (4029) being shuffled around the Russell yard over at Queen and Greenwood, assuming that by the time you arrive it hasn't been scrapped yet. With the fleet being in a transitional state right now the yard is full of dead cars, so if that's something you're interested in I'd recommend a trip over.

No, I didn't see 4215. The lines at Russell were short enough that by walking around the perimeter of the property, I could photo every ALRV on the west side of the yard. If the car is still in Toronto, I didn't see it.
In other news, 4103 is MIA. I witnessed it push 4094, looping around Russell, yesterday, and then about half an hour later I came back and their positions had been reversed and 4103 had its pole pulled down. Last ran May 9.

Seems strange that both cars would be not signed in, unless one of these AM trippers have not yet had trip data uploaded onto NextBus yet. But I presume this is good news for the fleet either way.
Meanwhile, here are a couple of photos of 4210 & 4251 in days gone by.
Toronto Transit Commission 4210 - 01 by Andrew P., on Flickr
Toronto Transit Commission 4251 - 02 by Andrew P., on Flickr

I'm sure there will be a media unveiling, but it will be to tout the environmental benefits of the bus, not to introduce a fringe group of oblivious clowns to quiet buses.
Everyone survived when there were trolley buses.

That cannot be. For one thing, it's been rainy/overcast all day, for another, those are not evergreen trees, so they wouldn't be green at this point, and finally, the grass in the photo is very dry, even though it's done very little except snow and rain all year.
Have a look for yourself. How would Google have been able to capture the image today and get it uploaded in time, and why would they claim the image is from July 2018?
https://www.google.com/maps/place/700+Arrow+Rd/@43.7467502,-79.5298242,3a,23.1y,272.9h,86.53t/data=!3m6!1e1!3m4!1smKYfRCfL6msp8YD2QT8gWg!2e0!7i16384!8i8192!4m5!3m4!1s0x882b3046ffad19a3:0x505a9b529c82e462!8m2!3d43.745728!4d-79.529601

What does "not functioning properly" mean?
There is nothing irregular happening to the streetcar fleet right now, it's just going through an immense shortage that is not going to ease up any time soon.
the 7900 buses are being used on the streetcar shuttles because they're not equipped with VISION. They are instead using TETRA radios just like the streetcars are. What the 1600s are doing there I don't know. Maybe they've decided to use them in tandem with the 79s.

It's also been done all over the former Czechoslovak countries, usually coupled with a full rebuild of the original body with new electronics.
https://commons.m.wikimedia.org/wiki/Category:Tram_1751_(Brno)#/media/File%3ABrno%2C_Moravské_náměstí%2C_BMUE_2004%2C_Tatra_K3R-N_č._1751.jpg
Of course, it also requires the base vehicle to be powerful enough. Considering that an ALRV has an unpowered center truck, and it already struggles with the Bathurst hill in unclear weather, it would likely require some major engineering work done to be able to haul around another section.